Distractions
I would argue 50% of the average person's day is spent in pursuit of pleasurable distractions. We feel compelled to pursue hobby's or activities that result in no net value increase. These distractions become a refuge for our weary minds and bodies. A meditative trance like state of attention focusing, results in a low but steady flow of endorphins. We become addicts to the mind numbing activities we recognize as fruitless. The power of distractions doesn't stop at mental habits either.
Physical daily exercise can also release a steady level of endorphins and put us into a "healthy" and positive frame of mind. Active folks go out of their way to push their bodies to improved performance by repeatedly going to the gym, running or swimming. Any athletic improvement is short lived though for without permanent sacrifice of time and energy our body's gravitate toward a lower fitness state. But some of us change our lives to include daily exercise, realizing the value of habitual activity isn't a goal that we meet but a way we can live our lives that benefits everything else we do.
Development
Over the course of years of exercise one's body feels uneasy when a day of activity is skipped. Our regular dopamine influx is missed, and the calm that comes after a normal workout escapes us. For our mental efforts a similar pattern sets in. If we continually pursue our passions we are positively reinforced with energy and enthusiasm. When we hit a roadblock the natural tendency is to give up and fall back into distractive habits.
Realizing that much like exercise, developing our mental pursuits requires life long sacrifice of time and energy is a key to getting past the urge to quit. There are times when the path we are on may be fruitless, and changing course is the only rational option. But giving up on our long term goals is not the solution we should seek.
Our greatest examples of motivation, enthusiasm and love for life are individuals who keep pushing their entire lives. They know the payoff is not the short term goal, but in the daily practice of pursuing their passionate hobbies, work, and athletic routines.
Now if only I could cut down on my distractions ;)